Alpha,beta-substituted acroleins and their preparation

ABSTRACT

Alpha,beta-substituted acroleins of the general formula I ##STR1## where A and B are identical or different and are each C 1  -C 4  -alkyl, naphthyl, biphenyl or phenyl which may be monosubstituted or polysubstituted by halogen, nitro, C 1  -C 4  -alkyl, C 1  -C 4  -alkoxy, C 1  -C 4  -haloalkyl, phenoxy or phenylsulfonyl, are prepared by a process in which a compound of the general formula III ##STR2## where A has the above meanings and R 1  and R 2  are identical or different and are each C 1  -C 4  -alkyl or together possess the carbon atoms required to complete a ring, is reacted with a phosphorus compound of the general formula IV or V ##STR3## where B the meanings stated above, R 1  and R 2  are as defined above and X.sup.⊖  is a halide ion, in the presence of a base. The alpha,beta-substituted acroleins can be further processed to give hydroxymethyloxiranes.

The present invention relates t alpha,beta-substituted acroleins, aprocess for their preparation, and their use for the preparation ofhydroxymethyloxiranes.

Hydroxymethyloxiranes are useful intermediates for the synthesis ofantimycotic and fungicidal azolylmethyloxiranes, which are described inEuropean Patent Application No. 94,564 of the Applicant. These compoundscan be prepared by reacting halomethyloxiranes, obtainable fromhydroxymethyloxiranes, with the appropriate triazoles or amidazoles orthe reactive derivatives of these compounds. According to EP-A-94 564,the hydroxymethyloxiranes can be prepared by epoxidation of thecorresponding allyl alcohols.

The preparation of hydroxymethyloxiranes by epoxidation of thecorresponding allyl alcohols is also described in other publications,for example in HoubenWeyl, VI/3, 371, in J. Org. Chem. 30 (1965), 2074,and in J. Am. Chem. Soc. 102 (1980), 5974 and ibid. 95 (1973), 6136.

The disadvantage of the known processes is that exposure to heatfrequently leads to E/Z isomer mixtures during the epoxidation.Moreover, some of the appropriate allyl alcohols are very difficult toobtain.

It is an object of the present invention to provide novelalpha,beta-substituted acroleins from which hydroxymethyloxiranes can beprepared stereoselectively and in very high yields, and a process forthe preparation of the said acroleins.

We have found that this object is achieved by providingalpha,beta-substituted acroleins of the general formula I ##STR4## whereA and B are identical or different and are each C₁ -C₄ -alkyl, naphthyl,biphenyl or phenyl which may be monosubstituted or polysubstituted byhalogen, nitro, C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, C₁ -C₄ -haloalkyl,phenoxy or phenylsulfonyl.

In the process for the preparation of the alpha,beta-substitutedacroleins of the general formula I, a compound of the general formulaIII ##STR5## where A has the above meanings and R¹ and R² are identicalor different and are each C₁ -C₄ -alkyl or together possess the carbonatoms required to complete a ring, is reacted with a phosphorus compoundof the general formula IV or V ##STR6## where B has the above meanings,R¹ and R² are as defined above and X⁻ is a halide ion, in the presenceof a base

The novel alpha,beta-substituted acroleins are further processed byepoxidizing them to give the corresponding formyloxiranes and reducingthe latter directly in the reaction mixture, i.e. in a one-vesselreaction, to give the hydroxymethyloxiranes of the formula II ##STR7##where A and B have the above meanings.

We have found, surprisingly, that the novel alpha,beta-substitutedacroleins can be converted to the hydroxymethyloxiranes in very highyields, some of these compounds being formed stereoselectively.

The conversion of the novel alpha,beta-substituted acroleins to themethyloxiranes is effected, if desired, in the presence of a solvent ordiluent and, if desired, with the addition of an organic or inorganicbase as a catalyst.

The preferred solvents include alcohols, e.g. methanol, ethanol,isopropanol, n-propanol, n-butanol, isobutanol, tert.-butanol orcyclohexanol, halohydrocarbons, e.g. methylene chloride, chloroform,carbon tetrachloride, dichloroethane or chlorobenzene, hydrocarbons,such as pentane, hexane, heptane, cyclohexane, toluene or xylene, andamides, e.g. dimethylacetamide or N-methyl-pyrrolidone. Other suitablesolvents are nitriles, e.g. acetonitrile, and sulfoxides, e.g.dimethylsulfoxide. Urea derivatives, e.g.1,3-dimethyl-3,4,5-tetrahydro-2 (1H)-pyrimidinone (DMPU), can also beused. Mixtures of these solvents may also be advantageously employed. Ifnecessary, the reaction is carried out with the addition of a phasetransfer catalyst, for example one of those described by E. V. Dehmlowand S. S. Dehmlow, Phase Transfer Catalysis (1980), Verlag Chemie.

Examples of suitable bases are alkali metal hydroxides, e.g. sodiumhydroxide or potassium hydroxide, alkali metal carbonates, e.g. sodiumcarbonate or potassium carbonate, alcoholates, e.g. sodium or potassiummethylate, ethylate, propylate, isopropylate, n-butylate, isobutylate,tert-butylate or cyclohexylate, and tertiary amines, e.g.trialkylamines, where the alkyl radicals are identical or different andmay be methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert.-butylor cyclohexyl. Aromatic amines, e.g. pyridine orN,N'-dimethylaminopyridine, may also be employed. Sodium hydroxide,potassium hydroxide, sodium carbonate and potassium carbonate areparticularly preferred.

The basic catalyst is advantageously used for the reaction in an amountof, for example, from 0.1 to 20, preferably from 0.5 to 10, mol percent,based on the alpha,beta-substituted acrolein of the general formula IIwhich is employed.

From 3 to 80, in particular from 20 to 60, particularly preferably 30,percent strength aqueous hydrogen peroxide solutions are suitable forthe epoxidation.

Suitable reducing agents are metal hydrides, e.g. diisobutylaluminumhydride or sodium, lithium or potassium hydride, borohydride orcyanoborohydride, as well as lithium aluminum hydrides of the generalformula

    Li Al (H).sub.m (OR).sub.n

where m is from 1 to 4, n is 4 - m and the radicals R may be identicalor different and are each in general alkyl, e.g. methyl, ethyl, propyl,isopropyl, n-butyl, isobutyl, tert.-butyl or cyclohexyl, or hydrogen, inthe presence or absence of a suitable catalyst, e.g. rhodium orruthenium. Sodium borohydride is particularly preferred.

The reaction is carried out in general at from -20° to +120° C.,preferably from -5° to +50° C., particularly preferably from 0° to +33°C., under atmospheric or superatmospheric pressure, continuously orbatchwise.

The epoxidation is carried out using, as a rule, equimolar amounts ofthe alpha,beta-substituted acrolein and H₂ O₂. However, it is alsopossible to use an excess of H₂ O₂, for example from 1 to 20%.

The reduction is preferably carried out using stoichiometric amounts ofthe reducing agent, although it is also possible to employ an excess,e.g. 0.5-20%.

When the reaction is complete, the end product can be isolated in aconventional manner, for example by extraction with a suitable organicsolvent, e.g. a chlorohydrocarbon, hydrocarbon, ester or ether, orparticularly preferably by direct crystallization from the reactionmixture, if necessary by adding water.

The rapid and virtually quantitative conversion of thealpha,beta-substituted acroleins of the general formula II to thehydroxymethyloxiranes of the general formula I is surprising in that theepoxyaldehydes formed as intermediates are very unstable and readilyreact further to give the corresponding acids or cleavage products as aresult of opening of the oxirane ring.

However, the one-stage procedure described for the use according to theinvention makes it possible to dispense with isolation of these labileintermediates. In a technically advantageous version of this process,the working-up step is substantially simplified in that an extractionand purification procedure can be dispensed with since in general theend product crystallizes out directly from the reaction mixture.

In the compounds of the general formulae I and II, the radicals A and Bare each preferably methyl, ethyl, propyl, isopropyl, butyl, sec.-butyl,isobutyl, tert.-butyl, 1-naphthyl, 2-naphthyl, p-biphenyl, phenyl,2-chlorophenyl, 3-chlorophenyl, 4-chlorophenyl, 2-fluorophenyl,3-fluorophenyl, 2-fluoro-6-chlorophenyl, 4-fluorophenyl, 4-bromophenyl,2,4-dichlorophenyl, 3,4-dichlorophenyl, 3,5-dichlorophenyl,2,6-dichlorophenyl, 3-chloro-4-methylphenyl, 2-methoxyphenyl,3-methoxyphenyl, 2,4-dimethoxyphenyl, 3,4-dimethoxyphenyl,4-methoxyphenyl, 4-ethoxyphenyl, 4-tert.-butoxyphenyl, 4-methylphenyl,4-ethylphenyl, 4-isopropylphenyl, 4-tert.-butylphenyl, 4-phenoxyphenyl,3-phenoxyphenyl, 3-nitrophenyl, 4-nitrophenyl, 3-trifluoromethylphenyl,4-trifluoromethylphenyl or 4-phenylsulfonylphenyl.

A and B in the compounds of the general formulae I and II are eachparticularly preferably methyl, tert.-butyl, phenyl, 2-chlorophenyl,4-chlorophenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl,2-fluoro-6-chlorophenyl, 4-bromophenyl, 2,4-dichlorophenyl or4-tert.-butylphenyl.

The prior art discloses processes for the preparation ofphenyl-substituted acroleins of the general formula I of the appropriatetype, but these processes give poor yields.

For example, the condensation of phenylacetaldehyde, which is verydifficult to handle, with benzaldehyde (in 15% excess) givesalpha-phenylcinnamaldehyde in a yield of only about 70% (Alder et al.,Ann. Chem. 596 (1954), 128. Undefined product mixtures which arerelatively difficult to separate are frequently formed, and these mixedaldol condensations are therefore of very little importance industrially(A. T. Nielsen and W. J. Houlihar, Org. Reactions 16 (1968); Houben-WeylVII/1, 76). In particular, the synthesis of the acceptor-substitutedalpha-phenylacroleins by this method is extremely unsatisfactory, sinceboth the preparation and the handling of the correspondingacceptor-substituted phenylacetaldehydes are extremely difficult.

Furthermore, the reaction of cinnamaldehyde with aromatic diazoniumsalts, e.g. p-chlorobenzenediazonium chloride, to givealpha-phenyl-substituted cinnamaldehydes gives extremely unsatisfactoryyields of about 35% (H. Meerwein et al., J. prakt. Chemie 152, 1935 andOrg. Reactions 24 (1973), 225)

According to the invention, a process for the preparation of thealpha,beta-substituted acroleins of the general formula I is provided inwhich a compound of the general formula III ##STR8## where A has themeanings stated in claims 1 to 3 and R¹ and R² are identical ordifferent and are each C₁ -C₄ -alkyl or together possess the carbonatoms required to complete a ring, is reacted with a phosphorus compoundof the general formula IV or V ##STR9## where P has the meanings statedin claims 1 to 3, R¹ and R² are as defined above and X.sup.⊕ is a halideion, in the presence of a base.

This reaction gives very high yields and is in some casesstereoselective. The starting compounds of the general formula III aredescribed in, for example, DE-A No. 34 07 005, and some of them inGerman Patent Application P No. 35 39 629.6 of the Applicant.

In the compounds of the general formulae III, IV and V, A and B have thesame meanings as in the compounds of the general formulae I and II. Aand B are each preferably methyl, ethyl, propyl, isopropyl, butyl,sec.-butyl, isobutyl, tert.-butyl, 1-naphthyl, 2-naphthyl, p-biphenyl,phenyl, 2-chlorophenyl, 3-chlorophenyl, 4-chlorophenyl, 2-fluorophenyl,3-fluorophenyl, 2-fluoro-6-chlorophenyl, 4-fluorophenyl, 4-bromophenyl,2,4-dichlorophenyl, 3,4-dichlorophenyl, 3,5-dichlorophenyl,2,6-dichlorophenyl, 3-chloro-4-methylphenyl, 2-methoxyphenyl,3-methoxyphenyl, 2,4-dimethoxyphenyl, 3,4-dimethoxyphenyl,4-methoxyphenyl, 4-ethoxyphenyl, 4-tert.-butoxyphenyl, 4-methylphenyl,4-ethylphenyl, 4-isopropylphenyl, 4-tert.-butylphenyl, 4-phenoxyphenyl,3-phenoxyphenyl, 3-nitrophenyl, 4-nitrophenyl, 3-trifluoromethylphenyl,4-trifluoromethylphenyl or 4-phenylsulfonylphenyl.

A and B are each particularly preferably methyl, tert.-butyl, phenyl,2-chlorophenyl, 4-chlorophenyl, 2-fluorophenyl, 3-fluorophenyl,4-fluorophenyl, 2-fluoro-6-chlorophenyl, 4-bromophenyl,2,4-dichlorophenyl or 4-tert.-butylphenyl.

The process for the preparation of the novel alpha,beta-substitutedacroleins is carried out in the presence or absence of a solvent ordiluent and particularly advantageously at from -10° to +130° C. in thepresence of a base.

The preferred solvents include alcohols, e.g. methanol, ethanol,propanol, isopropanol, n-butanol, isobutanol, tert.-butanol andcyclohexanol, hydrocarbons, e.g. pentane, hexane, heptane, toluene,xylene or cyclohexane, halohydrocarbons, e.g. methylene chloride,chloroform, carbon tetrachloride, dichloroethane or chlorobenzene, andethers, e.g. diethyl ether, methyl tert.-butyl ether, glycol dimethylether, glycol diethyl ether, dioxane and tetrahydrofuran. Polar aproticsolvents, e.g. dimethyl sulfoxide, hexamethylphosphorotriamide,acetonitrile, N-methylpyrrolidone, dimethylacetamide or1,3-dimethyl-3,4,5-tetrahydro-2-(1H)-pyrimidinone (DMPU), areparticularly preferred. Dimethylformamide is very particularlypreferred.

The reaction is advantageously carried out at from -10 to +130° C.,preferably from 0 to 60° C., particularly preferably from 10° to +30° C.

Examples of suitable bases are alkali metal hydrides, such as lithiumhydride, sodium hydride or potassium hydride, alkali metal amides, suchas sodium amide, potassium amide, or lithium diisopropylamide, as wellas alkali metal alcoholates, such as sodium and potassiumtert.-tuboxide, sodium and potassium methylate and ethylate andsodium-triphenylmethyl, potassium-triphenylmethyl, naphthalenelithium,naphthalenesodium and naphthalenepotassium.

The alkali metal alcoholates, particularly preferably sodium andpotassium methylate, ethylate, tert.-butylate and isopropylate, arepreferably used.

In carrying out the process, equimolar amounts of the ketone of thegeneral formula III and of the phosphorus compound of the generalformula IV or V are preferably used.

However, it is also possible to employ an excess of a reactant, forexample of a cheap reactant, e.g. an excess of up to 30%.

To isolate the alpha,beta-substituted acroleins of the general formulaII, an aqueous mineral acid, e.g. HCl or H₂ SO₄, is usually added andthe end product is, if required, extracted from the reaction mixturewith a suitable solvent, e.g. a hydrocarbon, chlorohydrocarbon, ester,ketone or ether. The compound of the formula II is particularlypreferably crystallized out directly from the reaction mixture, ifnecessary with the addition of water.

The starting compound of the general formula IV is usually obtained byreacting the corresponding halide with an alkyl phosphite (Houben-WeylXII/1, 433, and G. M. Kosolapoff, Org. Reactions 6 (1951), 276). Thephosphonates thus obtained can be employed in the Wittig-Horner reactionin pure form or as a crude product.

The phosphonium salts of the general formula V are obtainable byreacting triphenylphosphine with the corresponding halides (A.Maerckier, Org. Reactions 14, (1965), 270; G. Wittig, Angew. Chem. 68,(1956), 505 and Houben-Weyl V/2a, 185).

The omega,omega'-bisalkoxyketones of the general formula III areobtainable, for example, by reacting methylketones with sulfurylchloride or other conventional chlorinating agents in a conventionalmanner to give omega-dichloroketones, subjecting the latter to chlorideexchange with an alkali metal alcoholate in the appropriate alcohol as asolvent, and directly transacetalizing the product with a concentratedmineral acid, e.g. HCl (DE No. 34 07 005 A1).

The examples which follow illustrate the invention.

I. Preparation of the hydroxymethyloxiranes EXAMPLE 11-hydroxymethyl-1-(4-chlorophenyl)-2-phenyloxirane

70 g of 30% strength H₂ O₂ are added dropwise at 5°-10° C. to a solutionof 121 g of (E)-alpha-(4-chlorophenyl)-cinnamaldehyde in 400 ml ofmethanol and 3 ml of 25% strength NaOH. When the addition is complete,the mixture is stirred for a further hour at room temperature, afterwhich 4.625 g of NaBH₄ are added at 10°-20° C. Stirring is continued foran hour at room temperature, and 500 ml of H₂ O are added, after which116 g (89.2%) of 1-hydroxymethyl-1-(4-chlorophenyl)-2-phenyloxirane ofmelting point 90°-96° C. crystallize.

EXAMPLE 2(Z)-2-(4-chlorophenyl)-3-(2,4-dichlorophenyl)-2-(hydroxymethyl)-oxirane

13.5 g (0.043 mol) of(E)-2-(4-chlorophenyl-3-(2,4-dichlorophenyl)-acrolein are added to amixture of 0.65 g (0.005 mole) of potassium carbonate and 65 ml ofmethanol. 4.5 ml (5.0 g; 0.044 mole) of a 30% strength solution ofhydrogen peroxide in water are then added dropwise to the stirredmixture under nitrogen in the course of about 15 minutes at from 0° to5° C. The suspension is stirred for a further 30 minutes under N2 atfrom 0° to 5° C., and the temperature is allowed to increase to about25° C., while stirring. 0.95 g (0.025 mole) of sodium borohydride isadded to the stirred mixture in the course of about 10 minutes at from20° to 30° C. Thereafter, stirring is continued for a further hour atabout 25° C., after which 200 ml of distilled water are added. 13.3 g(0.040 mole; 93% of theory) of colorless crystals of melting point122°-127° C. are obtained; according to the ¹ H-NMR spectrum, these area mixture of the (Z) and (E) isomers in a ratio of about 85:15.

The said mixture of (Z)- and(E)-2-(chlorophenyl)-3-(2,4-dichlorophenyl)-2-(hydroxymethyl)-oxirane isrecrystallized from 150 ml of a 9:1 methanol/distilled water mixture.9.0 g (0.027 mole; 64%) of(Z)-2-(4-chlorophenyl)-3-(2,4-dichlorophenyl)-2-(hydroxymethyl)-oxiraneof melting point 137°-140° C. are obtained.

II. Preparation of the alpha,beta-substituted acroleins EXAMPLE 3(E)-(4-chlorophenyl)-cinnamaldehyde

A mixture of 500 g of diethyl benzylphosphite and 428 g ofomega,omega'-bismethoxy-4-chloroacetophenone is added dropwise to acooled solution of 270 g of potassium tert.-butoxide in 2 l ofdimethylformamide at 10°-20° C. When the addition is complete, 1 l of 2N HCl is metered in at 10°-25° C., while cooling with ice. After half anhour, a further 4 l of ice water are added, and the precipitated solidis filtered off under suction. 480 g (99%) of(E)-alpha-(4-chlorophenyl)cinnamaldehyde of melting point 70°-75° C. areobtained.

EXAMPLE 4 (E)-2-(4-chlorophenyl)-3-(2,4-dichlorophenyl)-acrolein

214 g (1.00 mole) of p-chloro-omega,omega-dimethoxyacetophenone areadded dropwise, in the course of ten minutes at from 20° to 24° C., to astirred mixture of 1,000 ml of dimethylformamide and 216 g (1.20 moles)of a 30% strength solution of sodium methylate in methanol. When thedropwise addition is complete, 312 g (1.05 moles) of diethyl(2,4-dichlorobenzyl)-phosphate are added in the course of 30 minutes atfrom 20° to 30° C., with further stirring. Thereafter, stirring iscontinued for 3.5 hours at about 25° C., and 2 l of distilled water arethen added to the reaction mixture. Stirring is continued for a further30 minutes, after which the product is filtered off under suction,washed with distilled water and dried in a drying oven under reducedpressure at 50° C. to give 350 g (0.98 mole; 98% of theory) of(E)-2-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-3,3-dimethoxyprop-1-ene inthe form of pale yellowish crystals of melting point 87°-90° C.

Thereafter, a mixture of 1,000 ml of distilled water, 500 ml ofmethanol, 50 ml (59.7 g; 0.62 mole) of concentrated hydrochloric acidand 350 g (0.98 mole) of(E)-2-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-3,3-dimethoxyprop-1-ene(I) is refluxed for 4 hours, while stirring. The mixture is cooled toroom temperature and 1,000 ml of water are then added, while stirring.300 g (0.96 mole; 98% of theory) of(E)-2-(4-chlorophenyl)-3-(2,4-dichlorophenyl)-acrolein are isolated inthe form of pale yellowish crystals of melting point 106°-109° C.

EXAMPLES 5 TO 67

The compounds listed in the table below were prepared, or can beprepared, by methods similar to those described in Examples 1 to 4. Thealcohols obtained in the form of an oil or resin were characterized insome cases via the corresponding tosylates.

                                      TABLE                                       __________________________________________________________________________     No.Example                                                                         A        B                                                                                      ##STR10##                                                                           ##STR11##                                                                             ##STR12##                               __________________________________________________________________________     5   C.sub.6 H.sub.5                                                                        2-FC.sub.6 H.sub.4                                                                     ..01  ..01    85-88°                             6   "        3-FC.sub.6 H.sub.4                                               7   "        4-FC.sub.6 H.sub.4                                               8   "        2-F, 6-ClC.sub.6 H.sub.3                                         9   "        2-ClC.sub.6 H.sub.4                                             10   "        4-BrC.sub.6 H.sub.4                                                                    170-173                                                11   4(Phenyl)-C.sub.6 H.sub.4                                                              2-ClC.sub.6 H.sub.4                                                                    106-108                                                                             153-155 99                                       12   2,4-Cl.sub.2C.sub.6 H.sub.3                                                            C.sub.6 H.sub.5                                                 13   "        2-FC.sub.6 H.sub.4                                                                     85-84 Resin                                            14   "        3-FC.sub.6 H.sub.4                                              15   "        4-FC.sub.6 H.sub.4                                              16   "        2-F, 6-ClC.sub.6 H.sub.3                                        17   "        2-ClC.sub.6 H.sub.4                                             18   "        3-ClC.sub.6 H.sub.4                                             19   "        4-ClC.sub.6 H.sub.4                                             20   "        2,4-Cl.sub.2C.sub.6 H.sub.3                                     21   "        2,6-Cl.sub.2C.sub.6 H.sub.3                                     22   2-ClC.sub.6 H.sub.4                                                                    C.sub.6 H.sub.5                                                 23   "        2-FC.sub.6 H.sub.4                                                                     Resin                                                  24   "        3-FC.sub.6 H.sub.4                                                                     Resin                                                  25   "        4-FC.sub.6 H.sub.4                                                                     Resin                                                  26   "        2-ClC.sub.6 H.sub.4                                                                    87    Resin   128-130                                  27   "        3-ClC.sub.6 H.sub.4                                                                    Resin                                                  28   "        4-ClC.sub.6H.sub.4                                              29   "        2,4-Cl.sub.2H.sub.3                                             30   "        2,6-Cl.sub.2C.sub.6 H.sub.3                                     31   "        4-BrC.sub.6 H.sub.4                                             32   2-FC.sub.6 H.sub.4                                                                     C.sub.6 H.sub.5                                                 33   "        2-FC.sub.6 H.sub.4                                              34   "        3-FC.sub.6 H.sub.4                                              35   "        4-FC.sub.6 H.sub.4                                              36   "        2-ClC.sub.6 H.sub.4                                                                    106-109                                                37   "        3-ClC.sub.6 H.sub.4                                             38   "        4-ClC.sub.6 H.sub.4                                             39   "        2,4-Cl.sub.2C.sub.6 H.sub.3                                     40   4-BrC.sub.6 H.sub.4                                                                    2-ClC.sub.6 H.sub.4                                             41   4-FC.sub.6 H.sub.4                                                                     C.sub.6 H.sub.5                                                 42   "        2-FC.sub.6 H.sub.4                                                                     89-92                                                  43   "        3-FC.sub.6 H.sub.4                                              44   "        4-FC.sub.6 H.sub.4                                              45   "        2-F, 4-ClC.sub.6 H.sub.5                                        46   "        2-ClC.sub.6 H.sub.4                                                                    85-88 103-105 104-105                                  47   "        3-ClC.sub.6 H.sub.4                                             48   "        4-ClC.sub.6 H.sub.4                                             49   "        2,4-Cl.sub.2C.sub.6 H.sub.3                                                             98-101                                                                             130     116-117                                  50   "        2,6-Cl.sub.2C.sub.6 H.sub.3                                     51   "        4-BrC.sub.6 H.sub.4                                             52   4-CH.sub.3C.sub.6 H.sub.4                                                              C.sub.6 H.sub.5                                                 53            2-FC.sub.6 H.sub.4                                                                     75-78 77-80                                            54            3-FC.sub.6 H.sub.4                                              55            4-FC.sub.6 H.sub.4                                              56            2-ClC.sub.6 H.sub.4                                                                    92    100-103 87                                       57            3-ClC.sub.6 H.sub.4                                             58            4-ClC.sub.6 H.sub.4                                             59            2,4-Cl.sub.2C.sub. 6 H.sub.3                                    60   4-BrC.sub.6 H.sub.4                                                                    4-BrC.sub.6 H.sub.4                                             61   3-Br, 4-FC.sub.6 H.sub.3                                                               2-FC.sub.6 H.sub.4                                                                     81-84 65-67                                            62   "        2-ClC.sub.6 H.sub.4                                                                    125-128       100-104                                  63   4-BrC.sub.6 H.sub.4                                                                    2-ClC.sub.6 H.sub.4                                             64   "        4-BrC.sub.6 H.sub.4                                             65   4-ClC.sub.6 H.sub.4                                                                    2-FC.sub.6 H.sub.4                                                                     80-83 90-92                                            66   "        2-F, 6-ClC.sub.6 H.sub.3                                        67   "        2-ClC.sub.6 H.sub.4                                             __________________________________________________________________________

We claim:
 1. A process for the preparation of an alpha,beta substitutedacrolein of the formula I ##STR13## where A and B are identical ordifferent and are each C₁ -C₄ -alkyl, naphtyl, biphenyl or phenyl whichmay be monosubstituted or polysubstituted by halogen, nitro, C₁ -C₄-alkyl, C₁ -C₄ -alkoxy, C₁ -C₄ -haloalkyl, phenoxy or phenylsulfonylwhich process comprises:reacting a compound of the formula III ##STR14##where A has the above meanings and R¹ and R² are identical or differentand are each C₁ -C₄ -alkyl or together possess the carbon atoms requiredto completa a ring, with a phosphorus compound of the formula IV or V##STR15## where B has the meanings stated above, R¹ and R² are asdefined above and X.sup.⊖ is a halide ion, in the presence of a base. 2.The process of claim 1, wherein the reaction is carried out in a solventor diluent at from -10° to +130° C.
 3. The process of claim 1, whereinthe reaction is carried out in a polar, aprotic solvent at from +10° to+30° C.
 4. The process of claim 1, wherein A and B are defined as setforth in claim
 2. 5. The process of claim 1, wherein A and B are definedas set forth in claim 3.